The long-term objective of this research is to expand knowledge about nocturnal asthma in youth so early identification of symptoms and targeted treatment are possible. The specific aims of this research are to: test model of the mechanisms by which sleep or sleep related changes in autonomic system functioning and inflammation trigger nocturnal asthma symptoms, sleep disruption, and cause daytime tiredness in youth; compare objective and subjective indicators of quantity and quality of sleep between youth with varying degree of nighttime asthma symptoms and youth not having asthma; and determine which subjective and objective measures or combination of measures of sleep are the best predictors of daytime tiredness and activity limitations in children having asthma. The study uses a 2 group (asthma/no asthma) experimental design. Fifty children (half with asthma) will participate with a parent. Parent and child will provide historical information on sleep and breathing problems at night; 7 days of diary report on the child s sleep, respiratory symptoms, pulmonary function and daytime tiredness and activity limitation due to breathing problems. The child will wear a wristwatch like band to monitor their movements during 7 nights of sleep at home and then come into the sleep laboratory or more in-depth monitoring of sleep and pulmonary function. The child's usual bedtime will be used during the first Bedtime will be delayed by 4 hours the second night to intensify sleep to in-laboratory sleep monitoring determine if this intensification has a detrimental effect on the child's pulmonary function. Innovative, non-invasive markers will be used to evaluate changes in autonomic system function (heart rate variability) and pulmonary inflammation (exhaled nitric oxide) during the in-laboratory sleep nights. Examining this data in the context of the adult data already reported in the literature should allow identification of possible development differences in the influence of sleep on nocturnal asthma symptom expression that would be worthy of further study. The information gained is critical to practicing health care providers who are working to quell rising ast morbidity particularly in ethnic minority children living in poverty.